/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.context.event;

import java.lang.reflect.Method;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import org.springframework.aop.support.AopUtils;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.expression.AnnotatedElementKey;
import org.springframework.context.expression.BeanFactoryResolver;
import org.springframework.context.expression.CachedExpressionEvaluator;
import org.springframework.context.expression.MethodBasedEvaluationContext;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.Expression;
import org.springframework.lang.Nullable;

/**
 * Utility class handling the SpEL expression parsing. Meant to be used
 * as a reusable, thread-safe component.
 *
 * @author Stephane Nicoll
 * @see CachedExpressionEvaluator
 * @since 4.2
 */
class EventExpressionEvaluator extends CachedExpressionEvaluator {

    private final Map<ExpressionKey, Expression> conditionCache = new ConcurrentHashMap<>(64);

    private final Map<AnnotatedElementKey, Method> targetMethodCache = new ConcurrentHashMap<>(64);


    /**
     * Create the suitable {@link EvaluationContext} for the specified event handling
     * on the specified method.
     */
    public EvaluationContext createEvaluationContext(ApplicationEvent event, Class<?> targetClass,
            Method method, Object[] args, @Nullable BeanFactory beanFactory) {

        Method targetMethod = getTargetMethod(targetClass, method);
        EventExpressionRootObject root = new EventExpressionRootObject(event, args);
        MethodBasedEvaluationContext evaluationContext = new MethodBasedEvaluationContext(
                root, targetMethod, args, getParameterNameDiscoverer());
        if (beanFactory != null) {
            evaluationContext.setBeanResolver(new BeanFactoryResolver(beanFactory));
        }
        return evaluationContext;
    }

    /**
     * Specify if the condition defined by the specified expression matches.
     */
    public boolean condition(String conditionExpression, AnnotatedElementKey elementKey,
            EvaluationContext evalContext) {
        return (Boolean.TRUE.equals(getExpression(this.conditionCache, elementKey, conditionExpression).getValue(
                evalContext, Boolean.class)));
    }

    private Method getTargetMethod(Class<?> targetClass, Method method) {
        AnnotatedElementKey methodKey = new AnnotatedElementKey(method, targetClass);
        Method targetMethod = this.targetMethodCache.get(methodKey);
        if (targetMethod == null) {
            targetMethod = AopUtils.getMostSpecificMethod(method, targetClass);
            this.targetMethodCache.put(methodKey, targetMethod);
        }
        return targetMethod;
    }

}
